1. Field of the Invention
This invention relates to a position calculating system and a haulage vehicle, and especially to improvements in or relating to the accuracy of a position calculation upon calculation of the position of a mining dump truck by dead reckoning that uses an inertial measurement unit (IMU).
2. Description of the Related Art
As a technology for the calculation of the position of a vehicle, there is employed a technology that like a GPS (Global Positioning System) or the like, measures its real coordinates on the earth. For this position calculation by the GPS or the like, the reception of positioning radio waves transmitted from geolocation satellites is indispensable.
However, the positioning radio waves may be blocked by a structural object or the like in the periphery of a travel route so that the position calculation by the GPS may be interrupted. As a technique for interpolating such a GPS position calculation, dead reckoning has hence been proposed. According to this technique, the state of motion of a vehicle is represented as a velocity vector on the earth or a local coordinate system by using a velocity calculated from a wheel rotational speed and outputs from an inertial measurement unit (IMU) including a gyro sensor and acceleration sensor, and the velocity vector is integrated to update the position of the vehicle.
In this dead reckoning, output values from an acceleration sensor and angular velocity sensor, which are disposed on a vehicle, are used so that the accuracies of these output values affect the accuracy of a position calculation. In U.S. Pat. No. 6,959,240 B2 and U.S. Pat. No. 6,895,313 B2, for example, technique are, therefore, proposed that detect an inclination of a vehicle by an acceleration sensor or the like and use this inclination to correct output values of the acceleration sensor and a gyro sensor.